Intake manifold



Oct. 10, 1939. w, MANNING 2,175,438

INTAKE MANIFOLD Filed Nov. 20, 1937 3nventor I y attorneys Patented Oct. 10, 1939 UNITED STATES 9ATENT OFFICE INTAKE MANIFOLD William H. Manning, Birmingham, Mich, as-

signor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application November 20, 1937, Serial No. 175,598

7 Claims.

This invention relates to internal combustion engines and more particularly to the fuel mixture system for such engines, with special reference to an intake manifold.

It is quite apparent that if fuel is not supplied substantially evenly at all times to the several cylinders of a multi-cylinder engine the performance thereof will be faulty and inefficient. The problem of designing a manifold to properly distribute the fuel to multi-cylinder engines, especially engines having six or eight cylinders, is quite complicated and involves many factors.

In some cases manifolds which are satisfactory from the standpoint of uniform distribution at one speed and/or load are entirely unfit under other conditions of service. In order for a manifold to be efficient it should effect a substantially uniform distribution of the fuel to the several cylinders over widely variable conditions of operation. I have found that if an intake manifold is built in accordance with the principles of my invention that the distribution of the fuel mixture to the cylinders of a multi-cylinder engine is improved over a wide range of speed and load and the performance of the engine is consequently increased.

and eight cylinders, over widely variable condi-.

tions of operation.

For a better understanding of my invention, reference is herein made to the accompanying drawing and detailed specification which illus-- trate and describe one form of my invention.

Figure 1 is a plan View with parts in section oi a manifold built in accordance with my invention.

Figure 2 is a sectional view taken on line 22 in Figure 1.

Figure 3 is a view taken substantially on line 33 in Figure 1.

or lesser number of cylinders.

In the drawing,

5 indicates an intake manifold having two substantially similar end branches 1 and two substantially similar inner branches 9, each of the branches communicating with a runner or header ll having a substantially flat floor l3.

At the junction of each of an inner and an end branch is a split I5 which assists in dividing the fuel stream and distributing the same to the branches 1 and 9, each of which leads to a plurality of engine cylinders.

Communicating with the runner or header II and extending at substantially a right angle thereto is a riser IT. My riser differs from commonly used forms in that the fuel mixture passage therein opens into the header through a 1 narrow slot extending across the header. In the specific embodiment shown in the drawing the riser has what may be termed a fish tail funnel shape. The passage is flared or widened in one plane and narrowed or tapered in a plane at 15- right angles thereto. Specifically, the fuel mixture passage changes from a substantially circular cross-section at [9 adjacent the point at which a carburetor (not shown) is connected to the riser to a substantially rectangular cross- 20 section at the junction 2| with the header.

In the embodiment of. my invention illustrated in the drawing the length of the rectangle is substantially equal to the width of the runner or header Ii and is somewhat less than twice the 25 diameter of the circular cross-section is, while the width of the rectangle is somewhat less than one-half of the diameter of the circular crosssection IS. The junction of the riser and the header is thus a. comparatively narrow slit or 0 slot extending transversely of the header across substantially the entire width thereof. v The change in shape of the fuel mixture passage in the riser is such that the cross-sectional area thereof remains substantially constant through- 5 out the length of the riser. Consequently, the restriction to flow in the riser is not materially changed from that ofv the usual riser of uniform or substantially uniform shape throughout. The center of the circular passage and the center of the rectangular slot are in substantial alignment and the change from one shape to the other is regular and devoid of sharp curves.

The results of a series of tests over widely variable conditions of speed and/or load show that 5 a manifold having a fish tail funnel shaped riser substantially improves the distribution of the fuel mixture to the several cylinders. The spark plug temperature method of determining the mixture distribution, as described in volume 66 of Automottive Industries on pages 450-454 and 486-491 in an article by Hector Rabezzana and Stephen Kolmar, may conveniently be used in determining the distribution characteristics of the manifold. The underlying theory as to the 55 reasons for the improvement in distribution is not, at present, fully understood. It was found by experiment that moving the usual riser for- Ward a small amount greatly improved the dis tribution to the rear half of the manifold, while moving the riser to the rear improved the distribution to the front half a corresponding amount. In each location it was found that the distribution in the half of the manifold toward which the riser was moved suffered, the greatest detrimental effect taking place in the cylinders nearest the riser. In an eight cylinder engine, for example, when the riser was moved forward cylinders three and four suffered and when the riser was moved to the rear cylinders five and six suffered, the change in each case being to make the cylinder nearest the riser lean and the adjacent one in the same port relatively rich. From the above experimental data it was thought that lengthening the engine with the consequent lengthening of the manifold would effect substantially perfect distribution. The lengthening of the engine for various reasons was undesirable and consequently it was decided to reduce the width of the riser opening in order to obtain as great a distance from the edge of the riser openings to port as possible. With this as a starting point, the present construction was evolved.

It is also believed that in the present riser an improvement is obtained by virtue of having no concentration point for condensed liquid particles of fuel. With the ordinary round riser opening fluid fuel particles tend to concentrate at the extreme point of the periphery of the opening, while in the construction comprising this invention a line of considerable length is provided. Whatever the reasons and theory may be, however, tests have shown that a great improvement in distribution over variable conditions of service is attained with a manifold having a riser constructed in accordance with the invention.

Surrounding the junction of the runner or header with the riser is a heater 23. The specific construction of the heater per se forms no part of the present invention and, therefore, is not shown in detail. Hot exhaust gases are forced to travel within the space 25 in the heater around the runner and riser and heat the fuel mixture in a controlled manner as will be readily understood. By constructing the riser as described more surface is exposed to the exhaust gases and the fuel mixture is heated more quickly in the warm-up period.

While I have shown and described my invention in connection with a manifold of the downdraft type, it will be understood that the principles of my invention may also be used in updraft manifolds. Many changes and modifications may be made in the embodiment of my invention shown and described without departing from the spirit of my invention and I do not wish to limit the patent granted thereon except as necessitated by the prior art.

I claim:

1. In an intake manifold for a multi-cylinder engine, a header and a riser opening into said header through a narrow slot extending across substantially the width of the header, said riser having a passage of' approximately the same cross-sectional area throughout its length.

2. In an intake manifold for a multi-cylinder engine, a header and a riser connected thereto, the entrance end of said riser being substantially circular in cross section and the junction with the header being a narrow slot extending substantially across the width of the header, said riser having a passage of approximately the same cross-sectional area throughout its length.

3. In an intake manifold for a multi-cylinder engine, a header and a riser connected thereto, the entrance end of the riser passage being substantially circular in cross section, said riser passage being of approximately the same cross-sectional area throughout its length and discharging into said header by means of a comparatively narrow slot extending across substantially the entire width of the header, said slot being of greater length and less width than the diameter of said circular cross section.

4. A manifold as in claim 3 in which the riser passage changes from the portion of circular cross section to the slotted portion substantially evenly and devoid of sharp curves.

5. In an intake manifold for a multi-cylinder engine, a headerfa riser connected thereto, the entrance end of said riser being substantially circular and the discharge end opening into the header by means of a slot of greater length and less width than the circular portion extending crosswise of the header, said riser having a passage of approximately the same cross-sectional area throughout its length, and a plurality of branches leading from the header to the cylinders of the engine.

6. In a downdraft intake manifold for an eightcylinder engine, a header, a riser connected thereto, the entrance end of said riser being substantially circular and the discharge end opening into the header by means of a narrow slot extending substantially across the entire width of said header, said riser having a passage of approximately the same cross-sectional area throughout its length, said slot being of greater length and less width than the diameter of the circular portion, and a pair of branches on each side of the junction of the riser and header, each branch adapted to conduct a fuel mixture from the header to a plurality of engine cylinders.

7. In an intake manifold for a multi-cylinder engine, a header, a riser connected thereto, the entrance end of the riser fuel passage being substantially circular and the discharge end opening into the header through a narrow slot of greater length and less width than the circular portion extending crosswise of the header, said fuel passage being of substantially uniform area throughout its length, and a plurality of branches leading from the header to the cylinders of the engine.

WILLIAM H. MANNING. 

